1. Field of the Invention
The present invention relates to a tape cassette loading system for a magnetic recording and reproducing apparatus and, more particularly, to a power circuit for supplying power to the driving motors of such a tape cassette loading system.
2. Description of the Prior Art
U.S. Pat. No. 4,664,337 discloses a video tape recorder (hereinafter abbreviated to "VTR") capable of operating with tape cassettes of different sizes, namely, a comparatively large tape cassette and a comparatively small tape cassette.
Shown respectively in FIGS. 3A and 3B are a large tape cassette and a small tape cassette. As shown in FIG. 3A, the large tape cassette 101 has right and left large reels 102 each having a reel hub and a pair of flanges formed respectively at the opposite ends of the reel hub. A magnetic tape 103 is wound on the large reels 103. The large tape cassette 101 is provided with an opening 104 formed substantially in the middle portion thereof with respect to a lateral direction between the front surface 101A and a bottom surface 101B, for leading a magnetic tape 103. A pair of guide rollers 105 are provided respectively at the right and left ends of the opening 104 to guide the magnetic tape 103 for movement across the opening 104.
As shown in FIG. 3B, the small cassette 107 has right and left small reels 108 each having a reel hub and a pair of flanges formed respectively at the opposite ends of the reel hub. A magnetic tape 109 is wound on the small reels 108. The small tape cassette 107 is provided with an opening 110 formed substantially in the middle portion thereof with respect to a lateral direction between a front surface 107A and a bottom surface 107B, for loading the tape 109. A pair of guide rollers 111 are provided respectively at the right and left ends of the opening 110 to guide the magnetic tape 109 for movement across the opening 110.
The center distance l.sub.1 between the large reels 102 of the large tape cassette 101 is greater than the center distance l.sub.2 between the small reels 108 of the small tape cassette 107. Since the opening 104 of the large tape cassette 101, and the opening 110 of the small tape cassette 107 are respectively for loading the magnetic tapes 103 and 109, the opening 104 and 110 are the same in shape and size.
In inserting a tape cassette through the cassette inserting opening in such a VTR capable of operating with the large tape cassette 101 and the small tape cassette 107, sensors discriminate the shape of the tape cassette, and then a driving motor for shifting the reels is actuated to operate according to the shape of the tape cassette in order to position the reels properly for the tape cassette.
That is, as shown in FIGS. 3A and 3B, a cassette holder 115 for carrying the large tape cassette 101 and the small tape cassette 107 to reel mounts has an inside measure corresponding to the outside measure of the large tape cassette 101. The large tape cassette 101 or the small tape cassette 107 is inserted in the cassette holder 115 located at a cassette receiving position through the cassette inserting opening 116 of the cassette holder 115 in a direction indicated by an arrow C. The large tape cassette 101, or the small tape cassette 107, is inserted in the cassette holder 115 as far as the front surface 101A, or the front surface 107A, thereof comes into abutment with stoppers 117 provided on the bottom plate 115A of the cassette holder 115 on a side opposite the cassette inserting opening 116, and thereby the front surface 101A, or front surface 107A, is positioned at a fixed front position P.sub.1. Guide grooves 118 and 119 are formed respectively in the respective bottom surfaces 101B and 107B of the large tape cassette 101 and the small tape cassette 107 along a center line passing the center position P.sub.2 corresponding to the respective centers with respect to a lateral direction of the large tape cassette 101 and the small tape cassette 107. In inserting the large tape cassette 101 or the small tape cassette 107 in the cassette holder 115, the guide groove 118 or 119 engages a guide rail 120 provided on the bottom plate 115A of the cassette holder 115 so as to extend along a line extending along the cassette inserting direction and passing the center position P.sub.2. Therefore, the large tape cassette 101 and the small tape cassette 107 are located in the cassette holder 115 at the same position corresponding to the center position P.sub.2 with respect to the position of the respective centers with respect to a lateral direction thereof.
Cassette discriminating sensors 122 and 123 which discriminate between the large tape cassette 101 and the small tape cassette 107, and generate electric signals are provided on the bottom plate 115 near the cassette inserting opening 116 of the cassette holder 115. A perfect cassette insertion detector 124 which detects the perfect insertion of the large cassette 101 or the small tape cassette 107, in the cassette holder 115 and generates an electric signal upon the detection of the perfect insertion of the large tape cassette 101 or the small tape cassette 107 in the cassette holder 115 is provided near the stopper 117 on the bottom plate 115A. When the large tape cassette 101 is inserted in the cassette holder 115 as shown in FIG. 3A, both of the cassette discriminating sensors 122 and 123 generate electric signals. When the small tape cassette 107 is inserted in the cassette holder 115, only the cassette discriminating sensor 123 generates an electric signal. Thus, the cassette discriminating sensors 122 and 123 decide whether the large tape cassette 101 is inserted in the cassette holder 115 or whether the small tape cassette 107 is inserted in the cassette holder 115
Referring to FIGS. 4A and 4B, a pair of reel mounts 128 are provided on the chassis 127 of the VTR 113. Each reel mount 128 is moved horizontally in directions indicated by arrows Z.sub.a and Z.sub.b between positions P.sub.5 and P.sub.6 respectively corresponding to the center P.sub.3 of each of the reels of the large tape cassette 101 and to the center P.sub.4 of each of the reels of the small tape cassette 107 to adjust the center distance between the reel mount 128 to the center distance l.sub.3 and l.sub.4. Right and left reel motors are secured respectively to the bottom surfaces of right and left sliding saddles 129 at the respective middle positions of the sliding saddles 129. The respective output shafts of the reel motors 130 project upright respectively from the upper surfaces of the sliding saddles 129. The reel mounts 128 are attached respectively to the upper ends of the output shafts of the reel motors 130. A pair of guide rails 132 and 133 are extended on the opposite sides of each reel motor 130 along the directions indicated by the arrows Z.sub.a and Z.sub.b. As shown in FIG. 5, the guide rails 132 and 133 are supported in a horizontal position respectively on substantially U-shaped supporting blocks 134 and 135 attached to the chassis 127 so as to extend respectively between the opposite ends 134A and 135B of the supporting block 134 and between the opposite ends 135A and 135B of the supporting block 135. Bearings 136 are fixed to the opposite ends 129A and 129B of each sliding saddle 129 for sliding engagement with the guide rails 132 and 133. Each sliding saddle 129 slides horizontally along the pair of guide rails 132 and 133 to move the reel mount 128 together with the reel motor 130 in the directions indicated by the arrows Z.sub.a and Z.sub.b between positions P.sub.5 and P.sub.6 respectively corresponding to the center P.sub.3 of each of the reels of the large tape cassette 101 and to the center P.sub.4 of each of the reels of the small tape cassette 107.
Referring to FIGS. 6A and 6B, a driving motor 139 is attached in a horizontal position to the chassis 127. The output shaft 140 of the driving motor 139 extends laterally in a gear box 141 attached to the chassis 127 and is supported rotatably in a pair of bearings 142 on the gear box 141. A pair of worms 143 are fixed to the output shaft 140 with a distance therebetween. The respective helix directions of the pair of worms 143 are opposite to each other. A pair of worm wheels 144 are supported fixedly respectively on a pair of upright rotary shafts 145 at the respective middle pats of the rotary shafts 145 in the gear box 141. Each worm wheel 144 is interlocked with the sliding saddle 129 with a driving arm 146 and a plate 147.
As shown in FIG. 7, each upright rotary shaft 145 is supported rotatably at the opposite ends thereof in bearings 157 on the gear box 141. A collar 148 is fitted on the upper end of the cylindrical center boss 144A of each worm wheel 144 for free rotation relative to the boss 144A. Each driving arm has one end fitted on the collar 148 for free rotation relative to the collar 148. An annular recess 149 is formed in each worm wheel 144 around the boss 144A. A lug 150 vertically extending downward from one end of each driving arm 146 is received in the annular recess 149. As shown in FIGS. 6A and 6B, an extension spring 151 is extended in a semicircular range in the annular recess 149. The extension spring has one end 151A connected to the lug 150 of the driving arm 146, and the other end connected to a stopper pin 151 planted upright in the worm wheel 144 in the annular recess 149. Thus, each driving arm 146 is biased rotatively by the extension spring 151 in a direction indicated by an arrow d seen in FIGS. 6A and 6B so as to be held in contact with the upper end of the stopper pin 152. Each plate 147 has one end 147A pivotally joined to a pivot pin 153 fixed to the other end 146B of each driving arm 146, and the other end 147B is provided with a slit 154. A pin 155 planted in one end 129A of each sliding saddle 129 is received in the slit 154 of the driving arm 147. An extension spring 156 extended along and over each plate 147 has one end 156A connected to the pivot pin 153, and the other end connected to the pin 155.
In a state where the reel mounts 128 are located respectively at positions corresponding to the respective centers P.sub.5 of the reels 102 of the large tape cassette 101 as shown in FIG. 4A, the driving motor 139 is not actuated when the large tape cassette 101 is inserted in the cassette holder 115 and thereby both the cassette discriminating sensors 122 and 123 generate electric signals. Then, the large tape cassette 101 inserted in the cassette holder 115 is carried by the cassette holder 115 to a cassette loading position indicated by imaginary lines in FIG. 4A, where the reels 102 of the large tape cassette 101 are seated respectively on the reel mounts 128.
Similarly, in a state where the reel mounts 128 are located respectively at positions corresponding to the respective centers P.sub.6 of the reels 108 of the small tape cassette 107 as shown in FIG. 4B, the driving motor 139 is not actuated when the small tape cassette 107 is inserted in the cassette holder 115 and thereby the cassette discriminating sensor 123 generates an electric signal. Then, the small tape cassette inserted in the cassette holder 115 is carried by the cassette holder 115 to a cassette loading position indicated by imaginary lines in FIG. 4B, where the reels 108 of the small tape cassette 107 are seated respectively on the reel mounts 128.
In a state where the reel mounts are located respectively at the positions corresponding to the respective centers P.sub.5 of the reels 102 of the large tape cassette 101, the driving motor 139 is actuated when the small tape cassette 107 is inserted in the cassette holder 115 to move the reel mounts 128 horizontally respectively in the directions indicated by the arrows Z.sub.a.
That is, in such a state, the output shaft 140 of the driving motor 139 rotates in a direction indicated by an arrow e in FIG. 6A. Then, since the respective helix directions of the worms 143 are opposite to each other, the worm wheels 144 are turned respectively in the opposite directions indicated by the arrows d in FIG. 6A through the same angle respectively by the worms 143. Then, each pin 152 of the worm wheel 144 tends to extend the extension spring 151, so that the driving arm 146 in contact with the pin 152 is turned in the same direction as the worm wheel 144 to push the pin 155 planted in the sliding saddle 129 through the plate 147 in a direction indicated by an arrow f in FIG. 6A.
Consequently, each sliding saddle 129 is caused to slide in the direction of the arrow Z.sub.a along the pair of guide rails 132 and 133 to shift the reel mount 128 horizontally to the position corresponding to the position P.sub.6 of the center of the reel 108 of the small tape cassette 107, and thereby the center distance between the reel mounts 128 is adjusted automatically to the center distance l.sub.4.
Upon the arrival of the reel mounts 128 respectively at the positions P.sub.6, the end 129A of each sliding saddle 129 is brought into abutment with the end 134B of the supporting block 134 to stop the sliding plate 129 as shown in FIG. 6B, while each worm wheel 144 is turned further in the direction indicated by the arrow d, so that each extension spring 151 is extended tensely in the direction indicated by the arrow d by the pin 152. Upon the detection of a rotational position of the worm wheel 144, a rotational position detector 158 generates an electric signal to stop the driving motor 139. Since the extension springs 151 are extended tensely, the sliding saddles 129 are positioned accurately respectively at positions corresponding to the positions P.sub.6 by the resilience of the extension springs 151. The worm wheels 144 are held stationary respectively by the worms 143 after the driving motor 139 has been stopped.
In a state where the reel mounts 128 are located respectively at positions corresponding to the respective positions P.sub.6 of the centers of the reels 108 of the small tape cassette 107 as shown in FIG. 4B, the output shaft 140 of the driving motor 139 rotates in the reverse direction to shift the reel mounts 128 horizontally in the directions indicated by the arrow Z.sub.b when the large tape cassette 101 is inserted in the cassette holder 115 and both the cassette discriminating sensors 122 and 123 generate electric signals.
That is, in such a case, the output shaft 140 of the driving motor 139 rotates in a direction indicated by an arrow g in FIG. 6B to turn the worm wheels 144 through the same angle respectively by the worms 143 in opposite directions indicated by arrows h. Then, the pin 152 planted in each worm wheel 144 pushes the driving arm 146 to turn the driving arm 146 in the same direction as the worm wheel 144. Then, the extension spring 156 is extended by the pivot pin 153 attached to each driving arm 146 to pull the pin 155 attached to each sliding plate 129 in a direction indicated by an arrow i.
Consequently, each sliding saddle 129 is caused to slide along the pair of guide rails 132 and 133 in the direction indicated by the arrow Z.sub.b, so that the reel mounts 128 are shifted horizontally respectively to positions corresponding to the position P.sub.5 of the centers of the reels 102 of the large tape cassette 101, whereby the center distance between the reel mounts 128 is adjusted automatically to the center distance l.sub.3.
In such a case, upon the arrival of the reel mounts 128 respectively at the positions corresponding to the positions P.sub.5, and end 129A of each sliding saddle 129 is brought into abutment with the end 134B of each supporting block 134 to stop the sliding saddle 129, while the worm wheels 144 are rotated further in the direction indicated by the arrow h. Consequently, each extension spring 156 is extended tensely in the direction indicated by the arrow i by the pin 153. Upon the detection of a rotational position of the worm wheel 144, another rotational position detector 159 generates an electric signal to stop the driving motor 139. In this state, the sliding saddles 129 are held in place by the tension of the extension springs 156, and thereby the reel mounts 128 are located accurately at the positions corresponding to the position P.sub.5 corresponding to the respective centers of the reels 102 of the large tape cassette 101. In this state, the worm wheels 144 are held stationary respectively by the worms 143.
Thus, in such a VTR capable of operating with both the large tape cassette 101 and the small tape cassette 107, a cassette mounting mechanism is actuated to mount the large tape cassette 101 or the small tape cassette 107 on the reel mounts 128 after the reel mounts 128 have been shifted to positions corresponding to the size of a tape cassette inserted in the cassette holder 115. Then, a tape loading mechanism is actuated to wind the magnetic tape 103 or 109 around the rotary drum. The cassette mounting mechanism is described in detail, for example, in U.S. Pat. No. 4,631,607. The tape loading mechanism is described in detail, for example in U.S. Pat. No. 4,620.245.
FIG. 8 shows a cassette mounting mechanism for shifting the cassette holder 115 to mount a tape cassette inserted in the cassette holder 115, namely, the large tape cassette 101 of the small tape cassette 107, on the reel mounts 128.
Upon the perfect insertion of the large tape cassette 101 or the small tape cassette 107 in the cassette holder 115, the perfect cassette insertion detector 124 generates an electric signal to actuate the driving motor, not shown, of a lifting mechanism in 9order to shift the cassette holder 115 downward in the direction indicated by the arrow a from the cassette inserting position to the cassette mounting position so that the reels 102 (or the reels 108) of the large tape cassette 101 (or the small tape cassette 107) engage the pair of reel mounts 128, respectively.
FIG. 9 shows the tape loading mechanism. As shown in FIG. 10, a pair of substantially J-shaped guide rails 210 and 211 are disposed so as to receive a rotary drum 205 therebetween. A curved first guide slit 212 is formed substantially in the central portion of each of the guide rails 210 and 211, and a second guide slit 214 is formed outside the first guide slit 212. A positioning pin 213 is planted in one end of each of the guide rails 210 and 211.
Sliding members 220 and 221 are provided for sliding movement respectively on the pair of guide rails 210 and 211. Each of the sliding members 220 and 221 is provided with an upright tape guide 230 and an inclined tape guide 231. As shown in FIG. 11, the sliding member 220 (the sliding member 221) is formed in the shape of a block, a first guide pin 223 to be received in the first guide slit 212 of the guide rail 210 (the guide rail 211) is attached to the lower surface of the sliding member 220 (the sliding member 221) at the substantially central portion of the same, and a second guide pin 224 to be received in the second guide slit 214 of the guide rail 210 (the guide rail 211) is attached to the lower surface of the sliding member 220 (the sliding member 221) at the outer corner of the rear end of the same. A U-shaped positioning recess 222 which engages the positioning pin 213 is formed in the front end of each of the sliding members 220 and 221. Each of the sliding members 220 and 221 is located at the front limit position with the positioning recess in engagement with the positioning pin 213. In FIG. 9, the respective front limit positions and respective back limit positions of the sliding members 220 and 221 are indicated by full lines and by broken lines, respectively. The upright tape guides 230 are set upright on the upper surface of the sliding members 220 and 221, respectively. The inclined tape guides 231 extend at an inclination substantially the same as that of the rotary drum 205.
The sliding members 220 and 221 are driven by a driving mechanism 235. Referring to FIGS. 9 and 12, the driving mechanism 235 comprises an upper ring gear 236 disposed below the rotary drum 205, a lower ring gear 237 disposed below the upper ring gear 236 and adapted to be driven in a direction opposite the direction of rotation of the upper ring gear 236, a connecting plate 240 having one end connected to the upper ring gear 236 by a spring 238, and the other end provided with a hole 239 receiving the first guide pin 223 of the sliding member 220, another connecting plate 240 having one end connected to the lower ring gear 137 by another spring 238, and the other end provided with another hole 239 receiving the first guide pin 223 of the sliding member 221, a worm 241, a worm wheel 242 engaging the worm 241, a main driving gear 234 coaxially joined to the worm wheel 242, an auxiliary driving gear 244 engaging the main driving gear 234 and the ring gear 236, an intermediate gear 245 engaging the main driving gear 245 and the ring gear 237, and a motor 247 for driving the ring gears 2367 and 237 reversibly respectively in directions opposite to each other. As the ring gears 236 and 237 are rotated reversibly respectively in opposite directions, the first guide pins 223 are moved along the first guide slits 212 of the rails 210 and 211 through the spring 238 and the connecting pins 240, respectively, while the second guide pins 224 are moved along the second guide slits 224 to slide the sliding members 220 and 221 along the guide rails 210 and 211, respectively.
In FIG. 9, full lines indicate a tape operating system in a state after the completion of tape loading operation. The tape operating system comprises tape guides 206A, 206B and 206C, a full-width erasing head 207, tape guides 208A, 208B and 208C, a sound head 209A, A CTL head 209B and a capstan 209C, which are arranged sequentially from the tape feeding side to the tape winding side. Preparatory loading of the tape on the tape guides on the tape feeding and tape winding sides is carried out by a pair of subloading mechanisms 250A and 250B.
The subloading mechanism 250A on the tape feeding side has a swing arm 253A pivotally supported on a pivot shaft 251A for swing motion and rotatably supporting a roller 252A on the free end thereof, and a crank arm 256A having one end rotatably supporting a worm wheel 254A, and the other end pivotally connected through a link plate 255A to the middle part of the swing arm 253A.
The subloading mechanism 250B on the tape winding side has a swing arm 253B having one end pivotally supported on a pivot shaft 251B for swing motion and the other end rotatably supporting a pinch roller 252B, and a crank arm 256B having one end rotatably supporting a worm wheel 254B, and the other end pivotally connected through a link plate 255B to the middle part of the swing arm 253B.
The respective worm wheels 254A and 254B of the subloading mechanisms 250A and 250B engage worms 257A and 257B mounted on a driving shaft 257 extending in front of the cassette mounting position in parallel to the tape cassette, namely, the large tape cassette 101 or the small tape cassette 107, at the opposite ends of the same. As shown in FIG. 12, the driving shaft 257 is rotated in the normal and reverse directions by a gear train having a gear 258A engaging the lower ring gear 237, gears 258B, 258C and 258D, and helical gears 259A and 259B.
When the tape cassette 101 or 107 is lowered onto the reel mounts 128, the upright tape guides 230 and inclined tape guides 231 of the sliding members 220 and 221 staying at the back limit positions are located inside the tape 103 or 109 contained in the large tape cassette 101 or the small tape cassette 107. In this state, the sliding members 220 and 221 are moved along the first guide grooves 212 and the second guide grooves 214 of the guides 10 and 11 by the driving mechanism 235 to the respective front limit positions. As the sliding members 220 and 221 slide toward the front limit position, the upright tape guides 230 of the sliding members 220 and 221 engage the tape 103 or 109 of the tape cassette 101 or 107 to pull out the tape 103 or 109 from the tape cassette 101 or 107 and to extend the tape 103 or 109 gradually along the outer circumference of the rotary drum 205.
Finally, the sliding members 220 and 221 arrive at the respective front limit positions to load the tape 103 or 109 in a predetermined helical position on the circumference of the rotary drum 205.
The foregoing VTR capable of operating with both the large tape cassette 101 and the small tape cassette 107 is provided with a tape cassette loading system including a plurality of driving motors, which are actuated sequentially in a period from the insertion of the tape cassette in the cassette holder 115 to the completion of tape loading operation. That is, the driving motor for shifting the reel mounts 128, the driving motor for shifting the cassette holder 115, and the driving motor for tape loading operation are actuated sequentially in that order. This conventional tape cassette loading system also has separate power circuits and control circuits individually for those driving motors, which entails various problems as follows.
First, provision of separate power circuits individually for the driving motors increases the size of the tape loading system, hence that of the VTR, and the increases the size of the VTR.
Secondly, although the driving motors need to be actuated sequentially for the series of steps of tape loading operation and must not be actuated simultaneously, it is possible that the driving motors are actuated simultaneously due to the malfunction of the separate power circuits, which may cause damages in the tape cassette.
Thirdly, since provision of separate power circuits and control circuits individually for the driving motors makes the constitution of the tape loading system, hence that of the VTR, complex and increases the cost of the VTR, in some conventional VTRs, control circuits for driving motors which need not be controlled very strictly for operation among the plurality of driving motors are omitted. In such a case, the motors which are not controlled by control circuits are unable to operate stably and accurately.